1. Field of the Invention
The present invention relates to an imaging apparatus, an image processing apparatus, and an exposure control method. More specifically, when a presentation image presented by a presentation device is detected from a captured image, a detection area is set at a position different from that of the detected presentation image. A detection value is calculated from an image signal in the detection area, and exposure control is performed in accordance with the calculated detection value, thereby obtaining a captured image in which the presentation image has appropriate brightness.
2. Description of the Related Art
Existing imaging apparatuses are designed such that, assuming that a desired object is at the center of the imaging range, large weight is placed on the center of an imaging range to detect brightness. The imaging apparatuses can therefore obtain a captured image with optimum brightness control of the desired object when the desired object is at the center of the imaging range.
However, brightness detection with large weight placed on the center of an imaging range may cause failure to obtain a captured image with optimum brightness control of the desired object if the desired object is off the center of the imaging range.
Such a phenomenon that prevents optimum brightness control of desired object is not does not allow may be caused when a presentation image presented by a presentation device, for example, an image displayed on a television device or an image projected on a screen by a projector, is photographed.
FIGS. 63A and 63B show images of, for example, a presentation scene, which are captured using an imaging apparatus. As shown in FIG. 63A, a captured image is generally composed so that a presentation image projected on a screen and a presenter are included in the imaging range. That is, the screen is not necessarily at the center of the imaging range. If the screen is not at the center of the imaging range, the imaging apparatus performs brightness control so that the object at the center of the imaging range, which may be different from the presentation image projected on the screen, has appropriate brightness. This may result in a captured image in which, as shown in FIG. 63B, the presentation image being projected whites out due to overexposure.
Furthermore, in the case where brightness detection is performed with large weight placed on the center of the imaging range, it may be difficult to obtain a captured image with optimum brightness control of the desired object even though the desired object is at the center of the imaging range. Such a phenomenon that prevents optimum brightness control of the desired object may also be caused in a case such as when the desired object has a low-luminance color as a base color such as black or dark blue. Materials used in presentations differ in design depending on the presenter and, for example, materials with a design using a base color of blue or black may be often projected. FIGS. 64A and 64B show images of, for example, a presentation image projected on a screen, which are captured using an imaging apparatus. As shown in FIG. 64A, when the presentation image is an image having a low-luminance color as a base color such as black, the imaging apparatus performs brightness control so that the dark image becomes bright. This may result in a captured image in which, as shown in FIG. 64B, a dark portion such as a black portion in the presentation image stands out so that bright portions such as white letters and figures in the presentation image become too bright to cause “white out”.
On the other hand, when a presentation image is dark, strobe light emission may be performed so that an image of the presentation image can be captured with appropriate brightness. However, the strobe light may be reflected and enter the imaging apparatus, which may cause difficulty in obtaining a captured image in which the presentation image has appropriate brightness.
FIGS. 65A and 65B show images of, for example, a presentation image displayed on a screen of a television device, which are captured using an imaging apparatus. As shown in FIG. 65A, when the presentation image is an image in a dark color such as black, strobe light emission is performed so that the presentation image has appropriate brightness. The strobe light may be reflected on the display screen of the television device, resulting in an captured image on which, as shown in FIG. 65B, the reflected strobe light is cast to cause difficulty in reading the characters and figures over the presentation image.
Further, dynamic changes in the design of presentation images in moving images or slide shows would cause an imaging apparatus to perform brightness control in accordance with the changes of scenes. Thus, difficult-to-read captured images such as images with variations in brightness will be obtained.
Japanese Unexamined Patent Application Publication No. 2007-195029 discloses an imaging apparatus in which a presentation imaging mode is provided to ensure that presentation materials can be photographed. In the presentation imaging mode, strobe light emission is restricted.